Instruction manual

Page 4 Chapter Two
Eagle 250 Upgrade Instructions, Rev. A00
The SCSI Floppy Drive
Most previous Alpha Micro computers, including the Eagle you’re upgrading from, used a separate
floppy disk controller to interface to a diskette drive. The Eagle 250 does not support any of the floppy
controllers used in previous Alpha Micro systems (the AM-210, 212, 214, or 219). Instead, it can use a
SCSI floppy drive, the AM-212-20.
The AM-212-20 attaches to the SCSI cable like any other SCSI device. Though it is a 3.5” diskette drive,
it uses a 5.25” mounting bay.
SCSI Tape Drives
Any SCSI tape drive which works in your current Eagle will also work in your upgraded Eagle 250. No
firmware revisions are necessary.
In order to warm boot from a Tandberg streaming tape drive, make sure you enter it as the alternate boot
unit ID in the CMOS Configuration Menu.
SCSI Hard Disk Drives
For optimum performance, use Wide SCSI-2 drives attached to the Wide (68-pin) SCSI connector.
Mixing SCSI-1, SCSI-2, and Wide SCSI-2 disks on the same bus tends to degrade performance and is
not recommended.
SCSI-2 Dispatcher
You must define a SCSI dispatcher in the system initialization command file. AMOS uses the dispatcher
to communicate with the SCSI controller chip. The dispatcher handles all communications with the SCSI
controller chip.
There are two versions of the SCSI dispatcher for the AM-138-10 board:
•
SCZ138.SYS is a high-performance version of the SCSI dispatcher, which supports command
queuing, synchronous transfers, multi-threaded operations, and scatter-gather operations.
•
SIM138.SYS is a simplified version of the SCSI dispatcher and does not support the high
performance features supported in SCZ138.SYS. You would use SIM138.SYS when making
warm boot tapes and for temporary situations with computers which have not had the AMOS
PIC code installed.
While both of these dispatchers support both narrow and Wide SCSI-2 devices, using the SCZ138.SYS
dispatcher increases system performance greatly, and allows you to use DCACHE and write cache
efficiently. SCZ138.SYS also supports several option switches to let you modify its performance, as
described in Chapter 5.
Please refer to Chapter 5 for instructions on enabling the Eagle 250’s SCSI dispatcher.